Working with Wood
A quick summary of Wood manufacturing techniques
Introduction to Woodworking
I'm hoping that you know what wood is but just to reiterate, wood is the structural fibrous tissue found in trees. Wood is extremely diverse and the properties of the material depend highly on the source of the wood. Some woods, like maple, are expensive but very strong and rigid. Others, like bass and balsa, are extremely light but very weak and flimsy. The wood you need depends on the application; for this project, we will most likely be using balsa wood for the airframe structure and (maybe) pine for an antenna tracker.
Few terms to define before we begin:
- Grain- The grain is the direction of the fibers in the wood. Straight grain runs along the longitudinal axis of the wood, and cross grain is any deviation from the straight grain. The grain is extremely important when working with wood in order to produce the finished result that you desire. When cutting across the grain, it is best to use a circular saw while a bandsaw is more suitable for cutting along the grain (also known as ripping). To get a smooth, clean finish it is best to sand with the grain. Going against or across the grain while usually scratch or chip the wood and it usually looks very ugly.
Figure 1: Axial, Tangential, and Radial Grain
- Grit- Grit refers to how rough the abrasive paper is. The value of the grit is inversely proportional to the particle size; a low grit will represent very coarse paper and a high grit will be finer.
Working with Wood
Before you begin, make sure that you've read over the Basic Lab Safety Rules.
All other lab safety rules apply.
Wear a face mask and safety glasses when necessary- Always wear safety glasses when cutting, drilling, or sanding wood to prevent foreign debris from entering the eyes. Most people don't typically use facemasks, but it is recommended if you are sanding in an enclosed space.
Inspect the wood before cutting, planing, or routing- Make sure the wood is free of nails and screws and other foreign metal objects before working with the wood. This could damage the equipment or cause user harm if caught in a machine.
Clean up your workspace after you are finished- Make sure to sweep, vacuum, and wipedown your workspace after you are finished cutting, drilling, or sanding wood. It is our responsibility to keep the lab clean for all!
Use a drill bit before inserting a screw- Always use a drill bit that is 1/16"-1/8" smaller than the corresponding screw. This will ensure a tight and long lasting fit while preventing the wood from splitting. Make sure to drill at least 1/8" from the edge of the wood and use an enter punch when possible.
Start sanding with a low grit- It is always best to start with a low grit abrasive paper (~30-50) and work your way up to higher grit. Depending on the desired finish, this could perhaps take up to 5 different grit levels to achieve the desired result. Do some research or ask a club member with wood working experience if you are unsure the paper required.
Raise the grain for ultra-smooth finish- Often time we may need a super smooth finish on the wood to reduce drag on the airframe. This can be achieve by a process known as raising the grain. To raise the grain, wet a cloth and rub it on the wood until the entire surface is damp. Make sure not to oversaturate the wood. Once the surface has dried, the surface will then be a bit bumpy. Sand the wood down to the desired finish.
Adhesives- The best liquid adhesive to use is standard wood glue. Make sure to spread the glue evenly on the one piece and place the other piece on top. Wipe away any glue that seeps out from the sides BEFORE setting it to dry. Use a few clamps to hold the pieces together while they dry- refer to the instructions on the back of the bottle for curing times. Make sure to place it out of the way so it does not get disturbed while curing.
Screws versus Nails- Nails and screws accomplish the same task but excel in different applications. Nails are better for wood frames when the joints and wood will be subjected to shifting and twisting. Screws have a higher tensile strength and are better for holding two pieces together and typically last longer than nails.
Written by T. Kantner
Last Edit: 09/17/2018 by T. Kantner